Butterflyfishes (Chaetodontidae)

Chaetodon lunula (Lacepede, 1802)

These colorful fishes are high-bodied, ovate, and strongly compressed with small mouths and a band of brush-like teeth in the jaws; there is no spine on the cheek at the corner of the preopercle (as seen in the angelfishes); the dorsal fin is continuous or slightly notched, with 6-16 strong spines and 15-30 soft rays, the anterior interspinous membranes deeply incised; the caudal fin varies from slightly rounded to slightly emarginate.

Many of the species feed on polyps of corals or on other coelenterates (those that are obligate coral-polyp feeders should not be collected for aquaria). Other butterflyfishes feed heavily on benthic algae and small bottom-dwelling invertebrates such as polychaete worms and crustaceans. Some such as the species of Hemitaurichthys are primarily zooplankton feeders.

Most butterflyfishes are solitary or occur in pairs; a few such as Heniochus diphreutes form aggregations. Those oriented to the bottom tend to form territories; some have relatively small territories while others wander over a large area of reef.

Many of the species have a black bar on the head which encloses the eye. Butterflyfishes are diurnal; they take cover in the reef at night, generally exhibiting a different color pattern from that of the day.

The family is well represented in Hawaiian waters by 24 species (two of these occur in deep water, and Chaetodon ulietensis is known from only two specimens, hence appears to be a waif). Two general Hawaiian names, kikakapu and lauhau, are applied to all but a few of the chaetodontids, as might be expected from their limited value as food fishes.

Fourspot Butterflyfish

Upper half of body dark brown with two white spots, lower half orange-yellow with a small brown spot on each scale; ocular bar orange, narrowly edged in black and blue; a narrow dark-edged blue band in dorsal and anal fins. Attains 6 inches (15 cm). Islands of Oceania, mainly in outer reef areas. Feeds primarily on coral polyps. Frequently seen in pairs.

Lined Butterflyfish

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